1. Field of the Invention
The present invention relates to printers.
In this specification, the term control character in a narrow sense shall be used to indicate ordinary control characters other than one or more characters subsequent to an escape character, and the term control character in a broad sense shall be used to indicate characters including control characters in a narrow sense and one or more characters subsequent to an escape character. The term "control character" used in the claims for the patent is the control character in a broad sense.
2. Description of the Prior Art
In order to print data output from a plurality of host computers, a printer system in which a plurality of host computers are connected to one printer through a plurality of host interfaces has been already developed.
In this type of printer system, when data is sent to the printer from each of the host computers at a time which differs for each host computer, the data can be normally printed. On the other hand, when data are simultaneously sent from two or more host computers, the data from the two or more host computers are mixed with each other because parallel processing is not performed, so that the data cannot be normally printed out.
An object of the present invention is to provide a printer capable of normally printing out, even when data are simultaneously sent to the printer from two or more host computers, the data.
Meanwhile, in a printer comprising a lot of functions, an escape character (ESC) is frequently used so as to diversify a control instruction in addition to independent ordinary control characters. The escape character is a character indicating that the succeeding one or more characters have different meanings from those of the ordinary control characters.
The meanings of the one or more characters subsequent to the escape character are not unified by manufacturers. Therefore, a printer comprising only a printing program corresponding to a command system for a particular manufacturer is not normally operated when a host computer made by another manufacturer is connected thereto.
In order to cause one printer to have general-purpose properties, therefore, a printer comprising a plurality of printing programs respectively corresponding to a plurality of command systems which differ in the meanings of one or more characters subsequent to an escape character and capable of selecting a printing program adaptable to a command system which a host computer as a sending source uses out of the printing programs by an operator operating a command system selecting key has been developed.
The above described printer has the disadvantage of requiring a laborious operation because the operator must select the program adaptable to the command system which the host computer as a sending source uses as well as not being normally operated when the operator erroneously performs the selecting operation.
An object of the present invention is to provide, in a printer comprising a plurality of printing programs respectively corresponding to a plurality of command systems which differ in the meanings of one or more characters subsequent to an escape character, a printer capable of automatically selecting a printing program adaptable to a command system which a host apparatus as a sending source uses.